Continuing advances in technologies have led to increasingly reducing the physical sizes of metal-oxide-semiconductor field-effect-transistors (MOSFETs). Magnitudes of supply voltages have been accordingly reduced to save power as well as to accommodate the reduction in the physical sizes of the MOSFETs, and respective threshold voltages (Vths) of the MOSFETs have also been reduced to mitigate performance degradation effects of reduced MOSFET gate voltages resultant from the reduction of supply voltages. As a result, a Bias Temperature Instability (BTI) effect, causing a change in the magnitude of the MOSFET's Vth, has become a concern.